Fusing is the process by which you take two identical cards and combine them to make a better card (usually of higher rarity)

 Fusing is the process by which you take two identical cards and combine them to make a better card (usually of higher rarity).

d3 items

 The cards you fuse together MUST be the exact same in terms of name or you cannot fuse them.  Additionally, with the exception of Black Widow at this point, no card can be fused more than once.  You can tell a card has been fused because it has a + after its name.

 

When you fuse two cards together the end result gets 5% of the total stats of the first card fused and 5% of the total stats of the second card fused.  Base Level, 

diablo 3 items

Experience, and Ability Level are NOT retained after a fuse and will be reset to 1.  Mastery is usually reset to 1 (some exceptions apply see below).